Pasture measurement - the new technology

With drones, satellites and aerial surveying used for crop monitoring, why are we not measuring our pasture from the skies? DairyNZ scientist Callum Eastwood attempts to get above the hype and estimate the potential for pasture measurement.

Plenty of farmers are still using the trusty plate meter, but for those who are keen on automating or exploring other ...
Robyn Edie

Plenty of farmers are still using the trusty plate meter, but for those who are keen on automating or exploring other options, there are new gadgets and technologies coming to the market.

Ten years ago, we thought we'd cracked it. Weekly pasture data delivered automatically from satellite images.

Measuring pasture biomass from space sounds like science fiction, but the Pastures from Space project I worked on in Australia proved it was science fact. It worked.

However, history tells us that plenty can go wrong between outer space and Earth, and in this project it was our weather that was the spanner (3D-printed of course) in the works.

The upshot was that the satellite images weren't good enough when it was cloudy or raining, which tends to occur a fair bit in spring when you really need pasture measurements most frequently. And with not enough satellites orbiting to catch the good days, it was back to the trusty rising plate meter for another decade.


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Fortunately, that setback in space hasn't stopped the search for new frontiers of technology and innovation; there have been several projects aimed at faster, cheaper and more accurate pasture measurement.

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So how far have we progressed with automating or at least stripping hours out of pasture measurement? And what are important attributes to look for in the tools currently available to help assess the pasture in your paddocks this spring?

I'm part of a team at DairyNZ studying precision agriculture, including pasture management tools, and what it might mean for the dairy industry. Much of the research is funded by the Transforming the Dairy Value Chain Primary Growth Partnership programme, a seven-year, $170 million innovation investment led by commercial partners, including DairyNZ and Fonterra, and partnered by the Ministry for Primary Industries.

If we take a ground-up view of the options, the most commonly used tools are plate meters, sward sticks, pasture probes and tow-behind devices, such as the C-Dax Rapid Pasture Meter and Jenquip Rapid plate meter. Some of these tools also come with GPS so you can map pasture cover and follow the same track week after week. Bluetooth connectivity is also possible so data can be uploaded to software before you even get back inside.

If you're interested in "automating" the measurement due to time constraints then the simplest option could be to use a contractor service that will measure the pasture for you. This may be cheaper than investing in a new innovation and at the end of the day, you just need the data when you want it.

If sitting on a quad bike towing a C-Dax isn't your idea of labour efficiency, then take a look at the C-Dax pasture robot that was on display at the National Fieldays this year. This four-wheeled autonomous vehicle with pasture sensors trundles around the farm following a GPS-mapped route, slipping under fences and collecting pasture data. Developed with Massey University, it looks promising but may be a year or two away from being available to buy off the shelf.

If we look at airborne options, we have cameras mounted on UAVs (drones) which are capturing some farmer attention and chequebooks. These can give you an indication of the relative amounts of feed on farm, in particular where there are areas of different growth.

Farmers have also used the information to estimate crop available, but we have yet to see a drone-based system with imaging calibrated to ryegrass cultivars that gives a suitable measure of pasture dry matter for pasture allocation and management.

Slightly further off the ground are fixed-wing aircraft mounted with cameras, which some companies are promoting to measure crop growth and plant stress. It is suggested that aircraft become a more economic option over areas greater than about 1000ha. The usefulness of the data comes back to the camera used and with fixed-wing aircraft there is potential to carry a much more sophisticated camera than with a drone.

This concept is being studied by another Primary Growth Partnership programme, Pioneering to Precision, led by Ravensdown, where an advanced sensor (camera) attached to a light aircraft is being used to remotely sense the nutrient status of hill-country pastures. This should translate to lower-cost options once the essential spectral attributes are known and calibrated.

Back in space, all is not lost. Better sensors are going up on satellites all the time and they are whizzing overhead far more often – at least daily. This gives us a better chance of finding gaps in Aotearoa's famous long, white shroud or using new methods to see through the cloud. We expect to see more progress in this area in the very near future.

What should farmers be looking for from pasture measurement technologies?

Farms often have different needs for pasture measurement depending on whether they are multi-farm businesses, owner-operators, sharemilkers or large corporate farms.

Our team recently examined the views of a group of New Zealand and international pasture management experts to determine the important attributes that farmers should expect from pasture measuring devices.

From this it was agreed that important functional requirements included: ease of use; low labour (eg less than 2 hours/100ha); data easily uploaded to any pasture software; and the device calibrated to our ryegrass/clover cultivars.

We identified three main decision-making contexts for pasture data: ranking paddocks; daily allocation of pasture; and identifying paddocks for pasture renewal. The data accuracy and frequency will be different depending on the end use of the data.

For ranking paddocks and assessing the farm average pasture cover, repeatability was considered to be a little more important than accuracy. Measurements need to be every 7-10 days in high pasture growth periods (eg spring) and the data needs to be available within 24 hours of measurement. This is particularly important to consider when subscribing to a contracted service.

For pasture allocation, the measurement needs to be more accurate and the data needs to be available within 2-3 hours but preferably immediately, eg so break fences can be erected while out in the paddock.

If new technology can help you nail these factors then you'll be a fair way towards growing more green – in your paddocks and farm bank balance.

Turning measurement into money - What can you do now to assess your pasture?

Frequency is king: Getting frequent data during high growth periods keeps your finger on the pulse. Augment formal data collection with regular assessment of residuals and the high cover paddocks.

Large farm and many staff? A tow-behind device may be most efficient. Set up your paddocks to make moving around easier and make sure you've got Health and Safety covered off.

Short on time? Think about contracting someone in to measure pasture for you.

Data doesn't make decisions: If you have taken the time to collect data, use it to make good decisions by getting more training for yourself and the team, using good grazing software or a farm consultant.

 - Stuff

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